The wine industry produces approximately fourteen billion bottles of wine per year. The bottled wines range in price from inexpensive table wines to very expensive, high-quality wines. The more expensive wines (i.e., from fifty dollars to thousands of dollars per bottle) are typically produced by a small number (presently, about two thousand) of high-end wineries that produce 200,000 to 80 million bottles of wine each per year.
Most bottled wines, both inexpensive and expensive, are sealed with cork stoppers. Cork stoppers include natural cork stoppers punched from strips of bark and less expensive molded or extruded agglomerated cork with natural cork discs on each end. Wine makers generally prefer cork stoppers for sealing their bottles to maintain the traditional wine-opening experience that consumers expect. Unfortunately, the use of cork stoppers can adversely affect the taste of wine, a characteristic commonly referred to as “cork taint.” Cork taint describes the “off” smell and taste imparted to wine from chemical contaminants such as 2,4,6-trichloroanisole (TCA) in the cork stopper.
The incidence of cork taint is sporadic and random, typically affecting 1–2% of bottled wines. Since cork taint takes effect after bottling, it cannot be detected until after a bottle has been opened. Cork taint manifests as very undesirable aroma and flavor characters that are imparted to bottled wines following contact with the cork. There is nothing more offensive and embarrassing for wine consumers and producers alike than for their wine to be rated as “spoiled.” For consumers, opening a cork-tainted bottle of wine can be socially embarrassing, particularly if it is an expensive bottle of wine. For wine collectors, the 1–2% incidence of cork taint imparts uncertainty about the entire wine collection. For producers, cork-tainted wine can damage their reputation, causing consumers to question the integrity and quality of their wine. Thus, there exists a need for a means to ensure the quality of cork stoppers used to bottle wines.
The chemical compound contributing most significantly to cork taint is TCA, which is implicated in more than 80% of cork-tainted wines. The production of TCA is the result of complex chemical mechanisms, including the conversion of chlorophenols to chloroanisole by common microorganisms, such as fungi, in the presence of moisture. Chlorophenols are typically used as pesticides and wood preservatives, and, consequently, they are common environmental pollutants. The uptake of even minute amounts of chlorophenol by the bark of a cork tree at any stage during its growth can yield corks that will produce cork taint in wine. Alternatively, cork taint can be the result of interaction between naturally occurring fungi in the tree bark and chlorine, a chemical commonly used to sanitize the cork. Cork, like any other wine input, therefore demands exhaustive quality control.
Quality assurance at every step of the cork stopper manufacturing process is a major concern of the cork industry. This concern has led to the implementation of the “International Code of Cork Stoppers Manufacturing Practices.” The code establishes quality-control standards throughout the production process and aims to provide guarantees to cork suppliers, wine producers, and bottlers that they have a product that is free from contamination.
In addition, premium cork suppliers also insist on rigorous quality-control testing of their cork stoppers for TCA. Current industry practices for quality-control testing of cork stoppers include sensory-based methods (i.e., olfactory detection or human experts) and chemical analysis (e.g., cork soaks and gas chromatography/mass spectroscopy). However, these testing procedures are limited to testing batches of cork stoppers (e.g., statistical sampling). For example, for every 100 million or more cork stoppers produced, only a half-million to one million are tested for TCA. The batch sampling approach does not eliminate the possibility that a TCA-tainted cork will be undetected during quality-control testing and subsequently used by a wine producer or bottler. Thus, there exists a need for a testing process that provides 100% testing of cork stoppers for TCA prior to bottling.
Another limitation of current testing methods is that they are expensive and time consuming. Further, sensory-based methods that rely on human experts are subjective, variable and exhaustible. Thus, there exists a need for a low-cost, reliable testing process that provides 100% testing of cork stoppers for TCA prior to bottling.
The wine industry, seeking to increase consistency and consumer loyalty, has investigated alternative quality-control procedures. One alternative is the application of electronic nose technology to quality-control testing at all stages of wine production, e.g., bottling. An electronic nose is a sensing device capable of producing a fingerprint of specific odors. Current technology includes electronic noses that use odor-reactive polymer sensor arrays and a pattern-recognition system (i.e., e-Nose) and gas chromatography coupled to surface acoustic wave sensors (i.e., z-Nose). In one example of polymer sensor arrays, the electronic nose uses a one-inch-square microelectrical mechanical systems (MEMS) chip containing 32 pinhead-sized receptors forming a sensor array. The receptors are constructed from a conductive carbon black material blended with specific nonconductive polymers (manufactured by Cyrano Sciences, Inc., Pasadena, Calif.). When the MEMS chip is exposed to a specific vapor, a corresponding receptor expands, temporarily breaking some of the connections between the carbon black pathways and thereby increasing the electrical resistance in the sensor. Signals from the sensors are electronically processed by a microprocessor that interprets the data by using the pattern-recognition system to identify and/or quantify a specific odor contained in the vapor.
Application of electronic nose technology to quality-control monitoring of agricultural products is exemplified in U.S. Pat. No. 6,450,008 to Sunshine et al., entitled, “Food applications of artificial olfactometry.” The Sunshine et al. patent describes a method and device for evaluating agriculture products and, more particularly, for assessing and monitoring the quality of food products by using electronic noses. The quality control monitoring device includes two sensor arrays for comparative monitoring of an agricultural product, e.g., before and after a processing step such as blending or mixing, or detection of a contaminant (e.g., microorganism) relative to a clean sample. However, the quality-control monitoring device is a single device that typically requires up to three minutes to obtain a result and to cycle to the next measurement, thus limiting the number of measurements that can be determined by a single device. Further, the existing devices are expensive, which precludes purchasing multiple instruments to achieve 100% testing of a product in a production process. Thus, there exists a need for a means to test 100% of all corks in a fast and cost-efficient way.
The introduction of a new technology platform (e.g., electronic nose technology) into an existing industry (e.g., the wine industry) is often a difficult and expensive process. Often, a new technology platform is implemented by high-end or specialty producers (e.g., high-end wine producers), for which the costs associated with the production of a quality product are generally higher and the benefits provided by the new technology are initially greater. However, this approach neglects the general consumer market (e.g., inexpensive table wines), in which the volume of products consumed offers greater potential returns. Thus, there exists a need for a means to test 100% of all corks at production speed that is cost-efficient and scalable to the general consumer market.